Printing hammers or heads have been driven by many different drives or prime movers. U.S. Pat. No. 3,726,213 shows a mechanism using an electromagnetic drive to attract an armature and drive a print head through an arc. The print strikes an inked tape to impress the character on a target surface. A return spring is used to restore the print head to its at rest condition. Naturally, the effect of this spring must be overcome by the attractive force of the magnet on the armature on the forward or drive stroke.
Belgian Patent No. 820,413 shows a printing hammer construction using straight line motor. Solenoid type action is generated by coils acting on a disc positioned between the coils. The disc has the printing hammer coaxially mounted thereon for reciprocatory movement along the coil and disc axis. A leaf spring is secured to the hammer body and the coil housing structure to restore the hammer to its at rest condition. Naturally, the effect of this spring must be overcome by the attractive force to complete the driving stroke of the hammer.